1. Field of the Invention
The present invention relates to a liquid ejection head, a liquid ejection apparatus, and a drive controlling method, more particularly to a structure and an ejection control technology of a liquid ejection head which is used in an inkjet recording apparatus and the like.
2. Description of the Related Art
As an example of an image forming apparatus, there is known an inkjet recording apparatus which has an inkjet head (ejection head) having disposed multiple nozzles (ejection elements) therein, and forms an image on a medium (ejection receiving medium) by ejecting ink from the nozzles while relatively moving the inkjet head and the medium.
For an ink ejection method in an inkjet head of an inkjet recording apparatus, there is known a piezoelectric method where a diaphragm (pressure plate) constituting a part of a pressure chamber is deformed by deformation of a piezoelectric element to change the volume of the pressure chamber, ink is introduced from an ink supply path into the pressure chamber when the volume of the pressure chamber is increased, and then the ink inside the pressure chamber is ejected as a droplet from a nozzle when the volume of the pressure chamber is reduced, and also a thermal inkjet method where ink in an ink chamber (pressure chamber) is heated to generate bubbles, and then the ink is ejected with the inflation energy generated when the bubbles grow.
When a pressurizing device, such as a piezoelectric element or a heater, which pressurizes ink ejected from the nozzle, is driven by means of a drive signal according to image data, ejection energy provided to the ink from the pressurizing device is generated. When the ejection energy acts on the ink inside the pressure chamber, the ink is ejected from the nozzle.
In the inkjet recording apparatus, ejection performance of the ink has an influence on the quality of the obtained image and print efficiency. Various efforts are made in an inkjet head in order to realize fast and stable ink ejection. For example, there is proposed a technology for performing fast and stable ejection in which a method for driving a piezoelectric element, which is a pressurizing device for pressurizing ink, is elaborated, when the ink is ejected from an inkjet head by means of the piezoelectric method.
Japanese Patent Application Publication No. 64-26454 discloses an inkjet recording apparatus, in which, after the main pulse for ejecting the ink is generated, a sub pulse with a power value that is less than or equal to the main pulse is generated to reduce the oscillation of the meniscus. In this inkjet recording apparatus, it is possible to eliminate the oscillation of the meniscus, which occurs in the vicinity of the orifice that leads to the liquid path, prevent incorporation of bubbles and leakage of the ink from the ejection port at times other than when the liquid path is driven, and obtain a constantly stable and favorable record image.
Japanese Patent Application Publication No. 11-42775 discloses an inkjet recording apparatus and ink ejection controlling method, in which, in the ink ejection cycles where the volume of the ink storage chamber is reduced in the ejection stages to eject the ink from the nozzles after increasing the volume of the ink storage chamber in the supply stages, when the volume of the ink storage chamber is reduced to a second value in the ejection stages after the volume of the ink storage chamber is increased to a first value in the supply stages, the volume of the ink storage chamber is maintained in a third value, which is between the first value and the second value, in the subsequent stage of the ejection stages, and then reduced to the second value. In such an inkjet recording apparatus and ink ejection controlling method, disturbance of the ink in the ejection stages can be prevented, so that the ink can be supplied smoothly in the subsequent cycle.
In the inkjet recording apparatus described in Japanese Patent Application Publication No. 64-26454, and in the inkjet recording apparatus and ink ejection controlling method described in Japanese Patent Application Publication No. 11-42775, the object is to control oscillation of the meniscus surface. These are effective particularly when using ink having low viscosity, but if the viscosity of the ink becomes high, oscillation of the meniscus surface becomes low, whereby the meniscus does not oscillate enough to affect ejection, thus it becomes no longer necessary to control the oscillation of the meniscus surface.
However, if the viscosity of the ink becomes high, the refill time (time for supplying ink into the pressure chamber) increases significantly due to the effect of viscosity resistance. Since the time for waiting until refilling is completed becomes long, this time for waiting is the rate-controlling factor, thus the problem is that the ejection speed (ejection frequency) is lowered.